I was from Ontario and they started with salt but eventually changed to calcium. I understand here in British Columbia it's a chemical and I've used it myself to control grass growth in gravel. It still causes rust though...and of course you can buy bags marked to the Windsor salt co. So like Warpig says, salt's still out there. I remember the grass medians in the highways all dead in the spring from this stuff. All the cars would be eaten through in four years.